1. Field of the Invention
This invention generally relates to a roller rung for a ladder-like cable bed or pipe bed to reduce traction force. More particularly, this invention relates to a roller rung for a ladder-type cable or pipe bed which can also bear substantial weight and can be assembled with improved easiness.
2. Prior Art
It is advantageous to utilize rollers in a cable bed to draw and lay a cable (or pipe) on the cable bed with reduced cable traction force, for such a cable is generally heavy and generates considerable friction with the cable floor or rungs when drawn on the cable bed.
U.S. Pat. No. 3,426,988 issued Feb. 11, 1969 to J. Bradley et al. discloses a cable installation roller. Production of this rather complicated roller and a complicatedly formed cable bed intended for this roller is costly. A cable bed should advantageously be as light as possible for easier and safer installation.
This cable bed together with such rollers and roller holding shafts will weigh substantially. Accordingly, installation and safe holding of this cable bed system in place will require an extra sturdy suspension system.
German Patent No. DAS 1,029,630 to H. Krantz (May 8, 1958) discloses a pipe holder roller. This roller is intended for a single pipe and does not provide a very large support power.
Japanese Laid-Open Utility Model Publication 62-172210 discloses a roller rung 11 to be incorporated in a plurality in a ladder-type cable bed 1 as shown in FIGS. 8 and 9. This cable bed 1 comprises a pair of elongated side rails 2, a plurality of support rungs 10 and a plurality of roller rungs 11.
The roller rung 11 comprises a plurality of roller disks 13 turnably mounted on an axial shaft 12 having a bolt hole 12a on each end. The roller rung 11 is mounted between the side rails 2 with two bolts 8 screwed through corresponding two holes provided in the side rails 2 into the bolt holes 12a from outside of the side rails 2.
The roller rungs 11 are expected to provide easier drawing of cables W shown in phantom onto the cable bed 1. For this reason, it may be advantageous to use many roller rungs 11 in a ladder-type cable bed 1 in place of support rungs 10.
However, it is much more costly to manufacture such a roller rung 11 than a simple support rung 10. Therefore, the number of roller rungs 11 which can practically be incorporated in a cable bed 1 is restricted. The number of total rungs (roller rungs 11 and support rungs 10) to be incorporated in a cable bed 1 is also restricted in view of manufacturing cost and total weight as well as friction generatable between a cable W and support rungs 10.
It is therefore advantageous to provide such roller rungs 11 with an additional function to also substantially bear cable weight to reduce the total number of rungs. However, a conventional roller rung 11 is fragile and cannot support as much weight as a support rung can.
Accordingly, it is an object of the present invention to provide an improved roller rung which can efficiently reduce cable traction force and can also assume the function of a support rung and bear substantial weight.
It is another object of the present invention to provide easy assembling of such a roller rung.
It is another object of the present invention to provide a cost effective cable bed by reducing the total number of rungs.